Gas heaters have burners which are adapted for heating by means of flames which are fuelled by gas supplies of the heaters. If the flame of such a burner were to become extinguished, for example due to wind, and if gas were to be supplied to such burners even after they became extinguished, the gas would not be consumed by the burners, and could thus pose a serious fire or explosion hazard, or could be hazardous if inhaled.
Many conventional outdoor gas heaters have ignition systems, and single thermocouple probes for actuating gas safety shut-off valves. Such valves operate to shut off gas supplies to the burners of the heaters in the event that the flames of the burners become extinguished.
The thermocouple probes operate according to the “Seebeck” principal. According to this principle, a micro-current is generated when a temperature differential is present in a closed circuit consisting of wires made of two dissimilar metals.
In the case of a heater gas safety shut-off valve, such a micro-current is used to operate solenoid valves which are for allowing, or shutting off, the supply of gas to the heater burner. Such a valve is biased to a closed position for preventing the supply of gas, but the micro-current of the thermocouple, if above a threshold current applicable to the solenoid, can maintain the solenoid valve in an open condition to allow the supply of gas to the heater burner.
It is the heat of the burner itself acting directly on the thermocouple which causes the temperature differential required for the thermocouple to generate the micro-current. If the flame of the burner is extinguished, that temperature differential will disappear or at least diminish, thus causing a reduction or termination of the micro-current, and this in turn causes the solenoid valve to close thereby shutting off the supply of gas.
Such gas heaters are typically used for outdoor heating. As a result, the heaters are often exposed to the weather, and can be affected by wind. In particular, during windy conditions, for example conditions in which the wind speed is around 5 to 12 kilometers per hour, the burner flame can flicker, and thus be unsteady, and produce less heat. If the heat sensed by the thermocouple reduces, this has the effect of lowering the micro-current generated by the thermocouple. If the current reduces to a value below the solenoid current threshold, the solenoid will close and this will shut off the supply of gas to the heater burner. An operator would then have to manually relight the burner, and this can be time consuming and inconvenient, especially if the heater needs to be relighted repeatedly, and if the heater is being used at busy venues such as restaurants, pubs and the like.
One way of addressing this problem is to move the heater to a less windy position. However, this itself can be inconvenient, and possibly even dangerous, and may result in heat not being provided in an area where it is most required.
It is an object of the present invention to ameliorate or overcome disadvantages of the prior art or to propose a useful alternative thereto.